His mother pulls back the handle, and the 11-year-old enters a room at the Patel Conservatory, where he greets his jazz teacher with an elbow-to-elbow bump.

Musicians and staff members at Patel know the routine and have already prepared for Billy's arrival. They have turned off vending machines with peanut-filled snacks and wiped down the keys of a baby grand piano. They allow his specially trained dog to sniff out every hallway, each room and every piece of equipment that Billy might get close to.

Billy has a severe peanut allergy. If he touches or even breathes in a minuscule particle of peanut, he could die.

This is why Karen Gensel rarely leaves her son alone anywhere. He mostly stayed home the first eight years of his life.

Then his parents bought Remy, one of few known allergen alert dogs in the area.

"Because of Remy, I don't have to be scared anymore about where peanuts are," Billy says. "I just have to be careful."

• • •

Billy was 18 months old when he got his first whiff of a cracker topped with peanut butter. He started swelling up. His father had to cut his shoes off him. Tests later confirmed a peanut allergy.

Breathing or touching or ingesting a tiny amount of peanut protein could cause Billy's throat to swell shut. He would have about 15 to 20 seconds to reach his antidote allergy medication, his mother said. Otherwise, he could die within minutes.

Peanuts are a common food allergen that cause more than their share of reactions because they are used in so many foods, said Dr. Patrick Klemawesch, an allergist and immunologist in St. Petersburg. From 1997 to 2007, peanut allergies more than doubled in the United States from 0.4 percent of the population to 1.4 percent, he said.

Still, researchers don't know the exact cause of peanut allergies or why such cases are on the rise. In 2007, approximately 3 million children under age 18, or about 4 percent, had some sort of food allergy, according to the Centers for Disease Control and Prevention. Every year, 30,000 people have severe reactions from food allergies, and 150 people die, agency statistics show.

Ten years ago, Debbie Hogan, a registered nurse in the Tampa Bay area, started a support group called Parents of Children with Food Allergies in West Central Florida. The group has grown to include about 250 members, she said.

Few facilities make accommodations for kids like Billy, the Gensels say. However, the Patel Conservatory at the Straz Center for the Performing Arts has worked with the family. Billy, who has played piano since age 3, joined a jazz class there two years ago.

Before he arrives, staff members wash hands and remove any food items left in rooms.

"Come on Billy," says director James Crumbly. "What song do you want to do?"

"Make Believe," Billy says.

Before he does, staffers again will wipe down the piano keys to make sure others haven't left behind peanut residue.

"Keeping students safe is a priority at the Patel Conservatory," said Wendy Leigh, vice president of education at the Straz.

Before Remy, Billy's mother decided to homeschool him rather than risk his exposure in an uncontrolled environment. Her husband, Ted, works for a company that services industrial scales. The couple bought the 57-pound black Labrador three years ago for $10,000.

Karen Gensel thinks the high cost keeps most people with severe allergies from getting service dogs. Others tell her allergen alert dogs are a gimmick. But Gensel says Remy has given her peace of mind and is worth the cost.

Remy had been rescued from a shelter in Fort Worth, Texas, a week before she was scheduled to be euthanized, Gensel said.

Dog trainer Leslie Staven taught her to hunt for peanuts. Staven would hide a peanut and reward Remy when she found it. It took about six weeks for Remy to find a peanut anywhere in a room. It took about seven months, however, before she could detect peanut residue after the nut was removed.

Staven even trained her to sniff Billy's plate in a restaurant, without drooling or nibbling.

Remy was the first dog trained by Staven, who moved from the Tampa Bay area and now lives in Montana. She has since trained about 15 more working dogs. She knows of only one other company in the nation that trains peanut allergen alert dogs.

She brought Remy to Billy's home near Wesley Chapel for two weeks of training before handing her over.

Staven and Billy's mother took Remy to the local library, where Remy alerted to peanut traces on books. They went out to eat, and Billy ate a restaurant meal that Remy deemed peanut free.

Remy loves to search. It's her favorite game.

Despite his allergy, Billy has traveled up and down the East Coast, watched 18 space shuttle launches, visited caves and museums, and attended Space Camp — all with Remy by his side.

"I was able to have my first corn dog at the fair," he said.

He went horseback riding and visited a crayon factory. He got to stay in a hotel for the first time and eat from a continental breakfast buffet.

"The look on his face was awe at being normal," his mother remembers.

Back at the Patel, he prepares to sit down with the band before a recent concert. But first Remy must walk around the piano. She sits with her nose level to the seat and doesn't move — not a good sign.

She smells something nutty.

"Good girl," Gensel tells her, before handing her a ball and thoroughly wiping the seat.

Finally, Billy sits down to play.

Elisabeth Parker can be reached at eparker@sptimes.com or (813) 226-3431.